Alternanthera dentata ‘Rubiginosa’, known as Alternanthera Red Threads or Ruby Glow, is a foliage plant recognized for its deep burgundy to reddish-purple leaves. Valued for its vibrant color and thread-like appearance, it adds a striking accent to garden designs. Its ornamental appeal comes primarily from its rich leaf coloration, not its inconspicuous flowers.
Understanding Alternanthera Red Threads
Alternanthera Red Threads exhibits a mounding and spreading growth habit, reaching a height of 8 to 12 inches with a spread of 12 to 18 inches. The foliage is slender and ranges from deep burgundy to reddish-purple, often emerging green in spring before intensifying in color. While it produces small, pale, button-like flowers, these are not its main attraction and are often hidden by dense leaves.
This plant offers versatility in the garden, serving as a groundcover, edging along borders, or as a vibrant addition to containers and hanging baskets. Its compact size and eye-catching color make it suitable for mass plantings or as a contrasting element in mixed arrangements. Alternanthera Red Threads thrives in warm climates and is grown as an annual in cooler regions, though perennial in USDA Hardiness Zones 9-11.
Cultivating Alternanthera Red Threads
Alternanthera Red Threads requires specific care to maintain vibrant foliage and healthy growth. The intensity of its leaf color depends on adequate light. It thrives in full sun, which promotes deep burgundy and red hues, though it can tolerate partial shade where its color may be less intense. In environments with high temperatures and intense light, scorching can occur.
The plant requires well-draining, fertile soil and consistent moisture. While it prefers slightly acidic to neutral pH levels (5.4 to 5.8), it adapts to various soil types as long as drainage is good. Consistent moisture is important, especially during hot weather, but avoid waterlogging to prevent root rot. Allow the top inch of soil to dry slightly between waterings.
Alternanthera Red Threads is a heat-loving plant and tolerates high humidity, suiting tropical and subtropical climates. It is sensitive to frost, so in cooler regions, it is grown as an annual or brought indoors for winter protection. For fertilization, a moderate feeding program is sufficient; a balanced, slow-release fertilizer can be applied in spring, or a constant liquid feed (175-225 ppm nitrogen) during the growing season. Over-fertilization can reduce color intensity.
Pruning maintains shape, encourages bushier growth, and prevents legginess. Pinching off growing tips promotes basal branching and a more compact form. Pinch 7 to 14 days after transplanting and as needed throughout the growing season.
Propagating Alternanthera Red Threads
Propagating Alternanthera Red Threads is achieved through stem cuttings. Late summer or spring are ideal times for cuttings. To prepare cuttings, select healthy stems and use a sharp blade to make clean cuts 1 to 2 inches long.
Remove leaves that would be submerged (if rooting in water) or buried (if rooting in soil). Cuttings can be rooted directly in moist soil, keeping the soil evenly moist but not saturated. Warmth and consistent humidity support root development. Cuttings are ready for transplanting within three to four weeks once roots are visible.
Addressing Common Issues
Alternanthera Red Threads can face several issues. If foliage color fades, it often indicates insufficient light, as full sun maintains vibrant hues. Wilting can signal underwatering, especially in hot conditions, while prolonged saturation of the soil can lead to root rot. Balance moist soil with avoiding waterlogging.
Nutrient deficiencies cause poor growth or less vibrant foliage; avoid over-fertilization. Common pests include spider mites and aphids. Regularly inspect plants for pests and address promptly with treatments like insecticidal soap or neem oil. While not prone to serious diseases, good air circulation and avoiding overly wet conditions prevent fungal issues.